1. Field of the Invention
The present invention relates generally to the field of linear motion devices and more particularly to a pneumatic or rodless cylinder having a carriage moveable relative to a body and a bearing means for supporting and guiding reciprocal movement of the carriage relative to the body. More specifically, the present invention relates to a bearing support and adjustment mechanism for a pneumatic or rodless cylinder.
2. Description of the Prior Art
A variety of linear motion devices currently exist in the art. Many are of the type which include a body, a carriage moveable relative to the body and bearing or a support means positioned between the carriage and the body for purposes of supporting and guiding the carriage during movement relative to the body. Pneumatic or rodless cylinders represent one such form of linear motion device. These devices generally include an elongated cylinder body, a piston reciprocally moveable within the cylinder body and a carriage connected to the piston either directly or indirectly for transferring reciprocal movement of the piston to a workpiece. Such devices also include various bearing or other means for supporting and guiding the carriage during its reciprocal movement relative to the cylinder body.
One such means is shown in U.S. Pat. No. 4,724,744 issued to Rosengren in which a pair of integral arms extend outwardly from the carriage and embody a pair of low friction rods for sliding movement relative to a bearing groove in the outer side surfaces of the cylinder. A further guide and support mechanism is illustrated in U.S. Pat. No. 4,878,390 issued to Hauser. Hauser discloses a linear positioning apparatus having a cylinder body, a carriage moveable relative to the body and a bearing means comprising a series of recirculating ball bearings for guiding and supporting the carriage relative to the cylinder body. A still further linear motion device is shown in U.S. Pat. No. 5,555,789 issued to Rosengren et al. which discloses a pair of separate and adjustable side rails for supporting the bearing means.
Regardless of the particular bearing means utilized to support movement of the carriage relative to the body, the selection and design of such bearing means necessarily involves the consideration of several factors including the nature of the cylinder body, the method by which such body is manufactured, the reaction of the body to dynamic forces during operation, the tolerances achievable with a certain cylinder body design, and the tolerances needed for a particular bearing design.
Pneumatic or rodless cylinders of the type to which the present invention has particular application, commonly embody cylinder bodies which are relatively long compared to the carriage dimensions. It is not uncommon for such cylinder bodies to be 20 feet long or longer. This makes it extremely difficult to maintain close tolerances along the entire body length. Further, most of these elongated bodies for these pneumatic cylinders are extruded rather than machined. This further compounds the problem of maintaining close tolerances. Still further, pressures within the cylinder which drive the piston cause the cylinder to repeatedly expand and contract during reciprocal movement of the piston, thus presenting further problems with respect to establishing and maintaining tolerances.
Accordingly, there is a need in the art for a linear motion device and more particularly for a pneumatic or rodless cylinder device having an improved bearing support structure which minimizes the need to maintain close tolerances during manufacture of the component parts, but which still facilitates easy assembly of the device with the desired close tolerances.
In contrast to the prior art, the present invention provides for a linear motion device having an improved bearing support and/or adjustment structure which facilitates manufacture of such device, including its component parts, with significantly greater flexibility with respect to maintaining tolerances, but which still results in a device having relatively close tolerances. More specifically, the preferred structure of the present invention includes an elongated cylinder body, a reciprocally moveable piston within the cylinder and a carriage mounted to the piston for reciprocal movement therewith. An improved linear bearing means is provided between the carriage and the cylinder or side rail for supporting and guiding the carriage relative to the cylinder during relative movement therebetween. In the preferred embodiment, the bearing means includes an elongated bearing member and a bearing support and adjustment means. The bearing support and adjustment means includes an elongated side rail with a first wedge surface and a wedge member with a second wedge surface. When assembled, the first and second wedge surfaces engage on another and means in the form of set screws or other threaded members are provided to move the wedge surfaces relative to one another. This in turn provides a means for adjusting the position of the bearing member along the length of the linear motion device. This structure enables the elongated cylinder body and the elongated side rail to be manufactured with a significantly greater degree of tolerance, but which, when assembled, results in a device with desired close tolerances. This in turn significantly reduces manufacturing costs and facilitates use of bearing mechanisms which would otherwise be impractical because of tolerance requirements.
Accordingly, it is an object of the present invention to provide a linear motion device having an improved bearing means for supporting and guiding a carriage for reciprocal, linear movement relative to a body member.
Another object of the present invention is to provide an improved pneumatic or rodless cylinder having a reciprocally moveable piston and a carriage mounted thereto together with an improved linear bearing support mechanism.
A still further object of the present invention is to provide an improved bearing system for a linear motion device including an improved bearing means facilitating greater manufacturing tolerances.
A still further object of the present invention is to provide a an improved mechanism for supporting and adjusting a bearing member in a linear motion device.
A still further object of the present intention is to provide a method of supporting and adjusting a bearing member in a linear motion device.
These and other objects of the present invention will become apparent with reference to the drawings, the description of the preferred embodiment and the appended claims.